The most valuable application of casein is in the food industry. It is used in an attempt to increase the nutritive quality of foodstuffs. However, such utilizations are often limited to adding edible fillers.
The main constituent part of whey is lactose for which there are numerous outlets, not only in the food industry, but also in the pharmaceutical or parapharmaceutical industry. Whey also includes proteins (serum proteins) which may also be of commercial value.
There are several ways of separating casein from whey. The method by which the largest volume of milk is processed is the "acid" method which consists in incorporating an acid (in particular hydrochloric acid) in milk in order to reach a pH (of about 4.5) at which the casein precipitates out and may be separated from the remaining whey. This technique suffers from numerous drawbacks. Regardless of the reagents used (hydrochloric acid or sulfuric acid), they are never totally free of heavy metals and other toxic substances which thus get into the milk. In addition, adding a strong acid into a high quality biological medium is an operation which is esthetically unsatisfactory and it also gives rise to ionic destabilization of the casein by increasing the ionic force in the medium. The resulting casein has therefore lost its phospho-calcium characteristics and can no longer constitute natural casein or "caseinogen", i.e. casein which has retained all its properties.
A second technique consists in obtaining casein by fermenting milk in order to produce an acid medium by generating lactic acid. Although, as a biotechnique, this technique is of higher quality than the preceding technique, fermentation profoundly modifies the structure of the proteins present in casein. Here again, the resulting casein cannot be considered as being in its natural state.
Mention may also be made of another technique, in which casein is produced by means of enzymes: the enzyme is casein rennin. As in the preceding case, the enzyme reaction has an effect on the protein structure of the casein phase. In addition, the casein is insoluble which makes subsequent processing or utilization more difficult.
All of these methods of production operate by adding a foreign body to milk, and this constitutes a first reason why it is impossible to isolate milk casein without modifying its structures.
A last technique consists in acidifying milk by treatment on ion exchanging resins. In principle, this technique is advantageous in that ideally it would avoid any foreign bodies being added to the milk, however its implementation suffers from numerous drawbacks. Firstly there is a major loss of substance retained by the resins which quickly become clogged and saturated. The process cannot be controlled from the microbiological point of view and resin regeneration by means of strong acids allows toxic substances such as heavy metals to get into the milk.
In addition to the drawbacks briefly outlined above of these methods with respect to casein, they also have non-negligible effects on the other product, namely is whey, making it more difficult or more expensive to make use of it.
The inorganic matter content of whey obtained by the acid method increases in proportion to the quantity of foreign acid added. The whey is thus unsuitable for direct utilization and in order to obtain a product that is of commercial value it is necessary to implement complex technologies (deionizing followed by filtering and concentration processes).
The presence of lactic acid in whey obtained as a by-product of producing lactic casein makes the whey unsuitable for any subsequent processing technology. In addition, lactic fermentation consumes lactose, thereby reducing the remaining quantity that is potentially available for constituting a valuable product.
Finally, whey obtained by enzyme processing requires major heat treatment in order to inhibit the residual enzyme activity, said heat treatment spoiling the qualities of the serum proteins which also constitute a valuable constituent part of whey.
The present invention seeks to provide a method of processing milk making it possible to extract its various constituent parts optimally, i.e. firstly retaining their initial properties and secondly under conditions of extraction that are commercially profitable.